From bae263ca12a52cbde1639ec7aacd577bf6d3e49e Mon Sep 17 00:00:00 2001
From: Zach Daniel <zach@zachdaniel.dev>
Date: Wed, 10 Apr 2024 13:46:44 -0400
Subject: [PATCH] improvement: support omitting generic action return types

---
 documentation/dsls/DSL:-Ash.Resource.md         |  2 +-
 documentation/topics/actions/generic-actions.md | 16 +++++++++++++++-
 lib/ash.ex                                      |  2 +-
 lib/ash/actions/action.ex                       | 15 +++++++++++++--
 lib/ash/resource/actions/action/action.ex       |  6 +++++-
 lib/ash/resource/dsl.ex                         |  2 +-
 test/actions/generic_actions_test.exs           |  4 ++++
 7 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/documentation/dsls/DSL:-Ash.Resource.md b/documentation/dsls/DSL:-Ash.Resource.md
index 066b2fad..d0b1af93 100644
--- a/documentation/dsls/DSL:-Ash.Resource.md
+++ b/documentation/dsls/DSL:-Ash.Resource.md
@@ -912,7 +912,7 @@ end
 
 ## actions.action
 ```elixir
-action name, returns
+action name, returns \\ nil
 ```
 
 
diff --git a/documentation/topics/actions/generic-actions.md b/documentation/topics/actions/generic-actions.md
index 6805ac19..0ea8867d 100644
--- a/documentation/topics/actions/generic-actions.md
+++ b/documentation/topics/actions/generic-actions.md
@@ -14,6 +14,20 @@ end
 
 A generic action declares its arguments, return type, and implementation, as illustrated above.
 
+> ### No return? No problem! {: .tip}
+>
+> Generic actions can omit a return type, in which case running them returns `:ok` if successful.
+>
+> ```elixir
+> action :schedule_job do
+>   argument :job_name, :string, allow_nil?: false
+>   run fn input ->
+>     # Schedule the job
+>     :ok
+>   end
+> end
+> ```
+
 ## Why use generic actions?
 
 The example above could be written as a normal function in elixir, i.e
@@ -51,7 +65,7 @@ action :priority, :integer do
 end
 ```
 
-> #### Returning resource instances {: .tip}
+> #### Returning resource instances {: .info}
 >
 > It sometimes happens that you want to make a generic action which returns an
 > instance or instances of the resource. It's natural to assume that you can
diff --git a/lib/ash.ex b/lib/ash.ex
index ed6683a0..14fb398c 100644
--- a/lib/ash.ex
+++ b/lib/ash.ex
@@ -1261,7 +1261,7 @@ defmodule Ash do
   """
   @doc spark_opts: [{1, @run_action_opts}]
   @spec run_action(input :: Ash.ActionInput.t(), opts :: Keyword.t()) ::
-          {:ok, term} | {:error, Ash.Error.t()}
+          :ok | {:ok, term} | {:error, Ash.Error.t()}
   def run_action(input, opts \\ []) do
     Ash.Helpers.expect_options!(opts)
     domain = Ash.Helpers.domain!(input, opts)
diff --git a/lib/ash/actions/action.ex b/lib/ash/actions/action.ex
index f977f6f2..b34bc72f 100644
--- a/lib/ash/actions/action.ex
+++ b/lib/ash/actions/action.ex
@@ -123,8 +123,15 @@ defmodule Ash.Actions.Action do
           case authorize(domain, opts[:actor], input) do
             :ok ->
               case call_run_function(module, input, run_opts, context, false) do
+                :ok when is_nil(input.action.returns) ->
+                  :ok
+
                 {:ok, result} ->
-                  {:ok, result}
+                  if input.action.returns do
+                    {:ok, result}
+                  else
+                    :ok
+                  end
 
                 {:ok, result, notifications} ->
                   remaining = Ash.Notifier.notify(notifications)
@@ -133,7 +140,11 @@ defmodule Ash.Actions.Action do
                     resource_notifications: remaining
                   })
 
-                  {:ok, result}
+                  if input.action.returns do
+                    {:ok, result}
+                  else
+                    :ok
+                  end
 
                 {:error, error} ->
                   {:error, error}
diff --git a/lib/ash/resource/actions/action/action.ex b/lib/ash/resource/actions/action/action.ex
index 30464d10..db6639fc 100644
--- a/lib/ash/resource/actions/action/action.ex
+++ b/lib/ash/resource/actions/action/action.ex
@@ -24,13 +24,17 @@ defmodule Ash.Resource.Actions.Action do
           touches_resources: [Ash.Resource.t()],
           constraints: Keyword.t(),
           run: {module, Keyword.t()},
-          returns: Ash.Type.t(),
+          returns: Ash.Type.t() | nil,
           primary?: boolean,
           transaction?: boolean
         }
 
   import Ash.Resource.Actions.SharedOptions
 
+  def transform(%{returns: nil} = action) do
+    {:ok, action}
+  end
+
   def transform(%{returns: original_type, constraints: constraints} = thing) do
     type = Ash.Type.get_type(original_type)
 
diff --git a/lib/ash/resource/dsl.ex b/lib/ash/resource/dsl.ex
index 3fca0749..fbd6ecb8 100644
--- a/lib/ash/resource/dsl.ex
+++ b/lib/ash/resource/dsl.ex
@@ -495,7 +495,7 @@ defmodule Ash.Resource.Dsl do
         @action_argument
       ]
     ],
-    args: [:name, :returns]
+    args: [:name, {:optional, :returns}]
   }
 
   @create %Spark.Dsl.Entity{
diff --git a/test/actions/generic_actions_test.exs b/test/actions/generic_actions_test.exs
index eff5a2f0..779db857 100644
--- a/test/actions/generic_actions_test.exs
+++ b/test/actions/generic_actions_test.exs
@@ -36,6 +36,10 @@ defmodule Ash.Test.Actions.GenericActionsTest do
           {:ok, "Hello #{input.arguments.name}"}
         end)
       end
+
+      action :do_nothing do
+        run fn _ -> :ok end
+      end
     end
 
     attributes do